The method of estimation of the effective roughness coefficient in the meandering channels based on numerical simulation

We propose the method for calculating the Manning effective coefficient that allows estimating the resistance to water flows in meandering river channels. The method is based on the numerical non-stationary models of the dynamics of shallow water in the irregular channel. We show the decrease in the average velocity of the fluid in the meandering channel in comparison with the straight-channel. On the basis of the N.B. Baryshnikov’s constructed dependence of the average velocity in the channel cross-section from the main value of the Manning coefficient, we determine the contribution to the flow resistance from meandering of the channel. The numerical model utilizes the Saint-Venant equations, which describe the dynamics of flows in the theory of shallow water and considers the irregular of the relief, external and internal forces, and the work of sources. For integrating the system of equations, we use the CSPH-TVD method and parallel technologies CUDA. With an increase in the degree of sinuosity of the channel, we have a decrease in the average velocity of the fluid in the section of the channel. Varying the main value of the Manning coefficient n0 in the straight-channel, we estimated the contribution to the flow resistance from the meandering of the channel and obtained the values of the effective Manning coefficient of the channel for various sets of parameters.